Several years ago, in our 2 level home in Botany Downs, we experienced some difficulty in keeping it warm due to cold air coming up the stairs from the entrance to the main living area. We also had difficulty with condensation forming on the windows during the Winter. Then we discovered the HRV system and all the benefits it could offer. With our concrete tile roof, we learned that there was a big source of warm air accumulating in the roof space during the daytime that could be filtered, by way of a fan down into the living areas. This proved to be a very economical form of heating and at the same time, almost totally eliminated all the condensation from our windows. Then, in the Summer we discovered an additional bonus in the evenings and during the hot, humid nights. As soon as the temperature of the air in the roof space dropped below that of the air in the house, we had a supply of fresh cooling air being filtered through the house, making sleep so much more comfortable. We later added a heat pump to the equation and found that the 2 systems compliment each other beautifully. So when we moved house almost 3 years ago, one of the first things we did was to install an HRV System and a heat pump and we have been living in comfort ever since.